The present invention relates to the general field of recycling water filtering systems used in a fish rearing environment and more specifically to such systems in which solid wastes, ammonia and other organic impurities harmful to fish are present and need to be eliminated on a continuing basis.
Reuse or recycling of water is becoming more desirable as the demand for sport and commercial fish, and therefore, the need for more efficient hatcheries and ponds is increasing. Untreated water drawn from rivers or lakes subject fish stocks to low quality water, unsuitable variations in flow rate, undesirable solid content, disease and uncontrolled temperature. Reuse and recycling of water can provide a substantial reduction in actual water requirements, optimization of fish growth by regulation of the water temperatures, control of disease by purification and optimized flow rates.
The vast majority of conventional filtering systems are employed in the same location as the fish habitat and as a result the filter media is placed either on the bottom of the tank or pond or otherwise maintained beneath the water area in which the fish breed and live. In this type of a rearing environment, it is the general practice to wash the filter media by using an upward flow of fluid cleansing action. Such method suffers the disadvantage of the accumulated solid wastes being carried upward and into the area in which the fish are located, resulting in the increased pollution of the water and increased difficulty in capturing and removing such waste.
A known use of a downflow directed filtering system in which the filter media consisted of a four foot layer of half inch to three inch rock covered with a one foot layer of one quarter to three-quarter inch of oyster shells proved to have extensive operational problems related to the efficiency of the filtering capability, inadequate water flow and undesired algae growth. Prior to the present invention there has not been a recycling, downflow directed, water filtering system available or known that satisfactorily and efficiently removes solid wastes, ammonia and carbon dioxide while at the same time provides sufficient dissolved oxygen for fish respiration.